package com.ll.util;

import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class MD5Security 
{
	private final static char[] hexDigits = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' };

	private static String bytesToHex(byte[] bytes) 
	{
		StringBuffer sb = new StringBuffer();
		int t;
		for (int i = 0; i < 16; i++) 
		{
			// 16 == bytes.length;
			t = bytes[i];
			if (t < 0)
				t +=256;
			sb.append(hexDigits[(t >>> 4)]);
			sb.append(hexDigits[(t % 16)]);
		}
		return sb.toString();
	}

	public static String code(String input) throws SystemException 
	{
		try 
		{
			MessageDigest md = MessageDigest.getInstance(System.getProperty("MD5.algorithm", "MD5"));
			return bytesToHex(md.digest(input.getBytes("utf-8")));
		}
		catch (NoSuchAlgorithmException e) 
		{
			e.printStackTrace();
			throw new SystemException("Could not found MD5 algorithm.", e);
		} 
		catch (UnsupportedEncodingException e) 
		{
			e.printStackTrace();
			throw new SystemException("Could not found MD5 encoding support.", e);
		}
	}

}
